Sheet metal stamping is an indispensable and significant process because it is well suited to mass production of a wide variety of parts. In the automotive industry, it is used to make several body parts such as doors, hoods and lift-gates. Several other industries such as the consumer appliance industry and the aerospace industry use sheet metal stamping extensively. It is highly desirable to ensure high quality standards for sheet metal stampings so as to avoid problems during subsequent assembly stages and to ensure that the form and finish meet requirements. A publication by Ananthakrishnan S., Agrawal S., Venugopal R., and Demeri M., entitled “RCS Based Hardware-in-the-loop Intelligent System Design and Performance Measurement,” in Proceedings of PerMIS 2002, NIST, Gaithersburg, Md., 2002, teaches design of an intelligent system with applications to manufacturing, based on a Real Time Control System (RCS) architecture. The Ananthakrishnan publication describes case studies on how the RCS architecture can be used in a flexible automation scenario, where traditional industrial control cards (hardware) do not provide adequate measures of performance. In addition, certain tooling concepts and blank-holder force actuator control units with individually controlled hydraulic cylinders have been developed to allow local control of metal flow into the die cavity during a stamping operation. Forces are applied on the sheet metal blank using hydraulic cylinders which are mounted on the lower bolster of a hydraulic press. In the known type of hydraulic or mechanical press, a ram depresses the piston of each of the hydraulic cylinders via the blank and tooling in a blank-holder force actuator area to raise the pressure inside the cylinders. The pressure is transferred to the blank. A closed-loop control system modulates the flow of hydraulic fluid from the cylinder. In known arrangements, pressure within the cylinder is difficult to control using commercially available PID (Proportional-Integral-Derivative) control cards. The few systems that are available presently are systems of hydraulic cylinders installed in the bed of the press (under the die). The hydraulic cylinders used to provide force actuation in known systems are placed in fixed locations in the bed of one particular press, and the force actuators are configured for operation in that press. In essence, these systems are not flexible and are customized for one particular press and thus tend to be very expensive.
The production of sheet metal stamping parts involves two distinct phases, namely, try-out and production. In the try-out phase, the die design is validated, and required process parameters (blank-holder force actuator forces, punch force etc.) are determined. Try-out is conducted by attempting to make the part and modifying the die and process parameters, until a part is consistently made within the required design tolerances. After successful try-out, the final die design and process parameters are transferred to a production unit that mass produces the part. In practice, try-out and production are typically conducted by different companies in different locations.
It is desirable to provide a system and method for sheet metal stamping that would offer reconfigurability utilizing a knowledge-base, as well as the most economy and flexibility in design, and in doing so, address the needs of both try-out and production.